linux-kernel - [RFC net-next PATCH 04/13] net: dsa: ocelot: suppress PHY device scanning on the internal MDIO bus

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Message-Id: <20250403181907.1947517-5-sean.anderson@linux.dev>
Date: Thu,  3 Apr 2025 14:18:58 -0400
From: Sean Anderson <sean.anderson@...ux.dev>
To: netdev@...r.kernel.org,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S . Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	Russell King <linux@...linux.org.uk>
Cc: linux-kernel@...r.kernel.org,
	Christian Marangi <ansuelsmth@...il.com>,
	upstream@...oha.com,
	Heiner Kallweit <hkallweit1@...il.com>,
	Vladimir Oltean <vladimir.oltean@....com>,
	Sean Anderson <sean.anderson@...ux.dev>,
	Alexandre Belloni <alexandre.belloni@...tlin.com>,
	Claudiu Manoil <claudiu.manoil@....com>,
	UNGLinuxDriver@...rochip.com
Subject: [RFC net-next PATCH 04/13] net: dsa: ocelot: suppress PHY device scanning on the internal MDIO bus

From: Vladimir Oltean <vladimir.oltean@....com>

This bus contains Lynx PCS devices, and if the lynx-pcs driver ever
decided to call mdio_device_register(), it would fail due to
mdiobus_scan() having created a dummy phydev for the same address
(the PCS responds to standard clause 22 PHY ID registers and can
therefore by autodetected by phylib which thinks it's a PHY).

On the Seville driver, things are a bit more complicated, since bus
creation is handled by mscc_miim_setup() and that is shared with the
dedicated mscc-miim driver. Suppress PHY scanning only for the Seville
internal MDIO bus rather than for the whole mscc-miim driver, since we
know that on NXP T1040, this bus only contains Lynx PCS devices.

Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>
Signed-off-by: Sean Anderson <sean.anderson@...ux.dev>
---

 drivers/net/dsa/ocelot/felix_vsc9959.c   | 4 ++++
 drivers/net/dsa/ocelot/seville_vsc9953.c | 5 +++++
 2 files changed, 9 insertions(+)

diff --git a/drivers/net/dsa/ocelot/felix_vsc9959.c b/drivers/net/dsa/ocelot/felix_vsc9959.c
index 940f1b71226d..2de12611ab57 100644
--- a/drivers/net/dsa/ocelot/felix_vsc9959.c
+++ b/drivers/net/dsa/ocelot/felix_vsc9959.c
@@ -1001,6 +1001,10 @@ static int vsc9959_mdio_bus_alloc(struct ocelot *ocelot)
 	bus->read_c45 = enetc_mdio_read_c45;
 	bus->write_c45 = enetc_mdio_write_c45;
 	bus->parent = dev;
+	/* Suppress PHY device creation in mdiobus_scan(),
+	 * we have Lynx PCSs
+	 */
+	bus->phy_mask = ~0;
 	mdio_priv = bus->priv;
 	mdio_priv->hw = hw;
 	/* This gets added to imdio_regs, which already maps addresses
diff --git a/drivers/net/dsa/ocelot/seville_vsc9953.c b/drivers/net/dsa/ocelot/seville_vsc9953.c
index eb3944ba2a72..28bcdef34a6c 100644
--- a/drivers/net/dsa/ocelot/seville_vsc9953.c
+++ b/drivers/net/dsa/ocelot/seville_vsc9953.c
@@ -901,6 +901,11 @@ static int vsc9953_mdio_bus_alloc(struct ocelot *ocelot)
 		return rc;
 	}
 
+	/* Suppress PHY device creation in mdiobus_scan(),
+	 * we have Lynx PCSs
+	 */
+	bus->phy_mask = ~0;
+
 	/* Needed in order to initialize the bus mutex lock */
 	rc = devm_of_mdiobus_register(dev, bus, NULL);
 	if (rc < 0) {
-- 
2.35.1.1320.gc452695387.dirty